<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        main {
            width: 90%;
            height: 600px;
            border: 2px solid black;
            position: relative;
            margin: 0 auto;
        }

        .login-box {
            width: 300px;
            min-height: 100px;
            border: 2px solid black;
            position: absolute;

            left: 50%;
            top: 50%;
            transition: all 1s;
            transform: translate(-50%, -50%);

        }
    </style>
</head>
<body>
<main>
    <div class="login-box">
        <label>
            <input type="text"/>
        </label>
        <label>
            <input type="password"/>
        </label>
        <button>登录</button>
    </div>
</main>

<script>

</script>
</body>
</html>